Light Brown Apple Moth (LBAM)
Epiphyas postvittana (Walker)
Screening and Identification Aid
S. Passoa1, M. Epstein2, T. Gilligan3, J. Brambila4, M. O’Donnell2
The light brown apple moth (LBAM) is a member of the
Tortricidae, a large family of moths (Lepidoptera) that includes
many pest species. In North America there are approximately 1200
species of tortricids, which are often referred to as “leafrollers”
because the larvae of some species feed inside a rolled leaf.
Most tortricid moths are small and brown with a wingspan of
approximately 10-30 mm. Although wing pattern can be used to
identify some tortricids, the forewings of LBAM are extremely
variable and wing pattern should not be used for identification.
This aid is designed to assist in the screening and
identification of LBAM adults collected from sticky traps in the
United States. It covers basic sorting of traps, first and second level
screening, and identification based on morphological characters.
Due to the extreme variability of LBAM adults, prior knowledge
of dissection techniques and Lepidopteran morphology may be
necessary to identify suspect LBAM specimens.
Figure 1: Outline of a light brown
apple moth in resting position.
Sorting
Traps should be initially sorted based on the presence of
moths of the appropriate size, color, and shape. Traps that contain
moths meeting all of the following requirements should be moved
to level 1 screening:
1)
moths are approximately 7-12 mm
long (forewing length) (Fig. 2 & 3)
2)
moths caught in sticky traps have
yellowish-brown to dark brown appearance
(Fig. 2)
3)
moths caught in sticky traps will
generally have standard appearance similar
to the outline shown in Fig. 1
Figure 2: Examples of LBAM
adults caught in a sticky trap.
Figure 3: Actual size (7-12 mm forewing
length) of an LBAM adult.
1) USDA-APHIS-PPQ, Columbus, OH; 2) Plant Pest Diagnostics Branch, California Department of Food & Agriculture, Sacramento, CA; 3) Colorado State University,
Fort Collins, CO; 4) USDA-APHIS-PPQ, Gainesville, FL
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Level 1 Screening
Moths that meet the sorting requirements should be
screened for suspect tortricids. Level 1 screening of individuals can
be performed without a genitalic dissection and covers couplets
1-4 of the screening key (page 4). Tortricid moths can be identified
by the following combination of characters:
1)
2)
3)
4)
4)
5)
Antennae simple, thread-like, and never
pectinate (feathery).
Tympanum absent. Members of the Pyraloidea may
appear similar but have a tympanum at the base of
the abdomen.
Labial palpi pointed and project forward. Some
families have labial palpi that curve upwards.
Maxillary palpi are very reduced and not visible in
tortricids. Maxillary palpi may be visible under
magnification in some commonly intercepted
pyralid species.
Proboscis (tongue) unscaled. Members of the
Gelechioidea and Pyraloidea have a scaled
proboscis.
Chaetosema (patch of bristle-like setae) present
above the compound eye. (Chaetosema may be
difficult to see without a high-quality microscope.)
Moths meeting the above criteria should be further
examined to determine if they are male or female. Males have
a single frenulum bristle on the hindwing and a slit where the
valves meet on the end of the abdomen. Females have multiple
frenulum bristles on the hindwing and hairy ovipositor lobes on
the end of the abdomen. If the specimen is determined to be a
female tortricid it should be moved to level 2 screening. If the
specimen is determined to be a male, the forewing should have a
fold at the base of the costal margin (Figs. 4). Males lacking this
costal fold can be discarded as not LBAM; males with a costal
fold should be moved to level 2 screening. Both male and female
LBAM have mottled hindwings (Fig. 6). This faint spider web-like
reticulation should be visible in a majority of LBAM specimens;
any specimens with mottled hindwings should be moved to level 2
screening.
Figure 4: Costal fold on a male LBAM.
Figure 5: Suspect tortricid on a
2 x 2 cm card cut from a sticky trap and
protected for storage or transport.
Figures 6: Spread LBAM adult showing
characteristic mottled hindwing.
Suspect tortricids may be sent to level 2 screening on individual 2 x 2 cm cards cut from the sticky trap.
Cards can be safely transported in small jars or vials (Fig. 5) either singly or back-to-back to avoid damaging
the specimens. If jars or vials are not available, pin the card to a foam bottom mailing box with several insect
pins. Screeners that have more than two suspect LBAM adult specimens in a single trap should send the whole
trap rather than cut out individual specimens if using a Centralized Identification Laboratory. Samples must be
properly labeled with trap number, location, collection date, and any other information required by the LBAM
National Survey Guidelines.
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Level 2 Screening
Suspect tortricids should be cleaned and dissected to
identify suspect LBAM specimens. Details on cleaning specimens
caught in sticky traps can be found in the following article:
Miller, R. S., S. Passoa, R. D. Waltz & V. Mastro. 1993.
Insect removal from sticky traps using a citrus oil
solvent. Ent. News 104(4): 209-213.
Cleaned specimens should be pinned and the abdomen
removed for dissection. The pinned specimen, and all appropriate
data, should be retained as a voucher along with a label that
associates the pinned specimen with the separated abdomen.
Standard dissection procedures for Lepidoptera are outlined in
Clarke (1951) and Robinson (1976). Dissected tortricids can be
screened based on the following characters. Level 2 screening
covers couplets 4-6 of the screening key (page 4).
Figure 7: Complete male
LBAM genitalia.
Males
Male LBAM genitalia (Fig. 7) can be distinguished based
on a combination of two characters:
1)
2)
Uncus spatulate (spoon-shaped) (Fig. 8).
This character should not be used alone since
several common non-target tortricids
(Choristoneura rosaceana and many Clepsis
species) have a similarly shaped uncus.
Figure 8: Male LBAM spatulate (spoonshaped) uncus (phase contrast image).
Valva with a membranous lobe on the apex (Fig. 9).
This is the best diagnostic character for male
LBAM, although the lobe may vary in size and may
be difficult to see in some specimens. Questionable
specimens should be sent forward for identification.
Females
Female LBAM are difficult to screen. LBAM has a long
straight ductus bursae and a corpus bursae with a signum, but this
combination is not unique. A common non-target in California,
Clepsis peritana (garden tortrix), has a spiral ductus bursae; this
character can often be seen by brushing scales off the abdomen
while the specimen is in alcohol or a cleaning agent. Females with
characters similar to those in Figs. 10-11 should be sent forward
for identification.
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Figure 9: Membranous lobe on the apex
of the male LBAM valva (phase
contrast image)
Key to Screen LBAM Suspects in the
United States
The following key covers both level 1 and 2 LBAM
screening for suspect tortricids. Sticky traps normally capture only
males moths, although California LBAM traps capture female
tortricids more often than expected. Both sexes of moths are
included along with notes to help the identifier with each couplet.
1.
Abdominal or thoracic tympanum present; antenna
pectinate; labial palpi upturned; proboscis scaled or absent;
moths not about 7-12 mm long ................... Not LBAM
1’.
Abdominal and thoracic tympanum absent; antenna simple;
labial palpi pointed and projecting forward; proboscis not
scaled; moths about 7-12 mm long ................................2
2.
Chaetosema absent ....................................... Not LBAM
2’.
Chaetosema present or condition unknown
3.
Males ..............................................................................4
3’.
Females ..........................................................................6
4.
Costal fold absent; uncus tubular ................ Not LBAM
4’.
Costal fold present; uncus spatulate...............................5
5.
Membranous lobe from apex of valve
absent ........................................................... Not LBAM
5’.
Membranous lobe from apex of valve
present ................................................... LBAM Suspect
6.
Ductus bursae in a spiral; signum
absent ........................................................... Not LBAM
6’.
Ductus bursae straight, never in a spiral;
signum present ...............................................................7
7.
Ductus bursae no more than 2-3 times as long as the corpus
bursae and entire bursae 1/2 the length of the abdomen or
less................................................................ Not LBAM
7’.
Ductus bursae 4-5 times as long as the corpus bursae
and entire bursae (ductus + corpus bursae) at least 2/3
length of abdomen................................. LBAM Suspect
Figure 10: Female LBAM
papillae anales and sterigma.
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4
Figure 11: Female LBAM hook-shaped
signum in corpus bursae.
Notes: 1) In California, crambid moths in the genus Achyra
are often captured. Based on previous surveys in the Eastern
United States in the 1990’s, LBAM traps have commonly
captured a species of Pyrausta. Therefore it is particularly
important to understand how to separate Crambidae from
Tortricidae in any LBAM survey. 2) If the chaetosema
are clearly absent, this can be used to rule out LBAM. If
chaetosema are present, or the user is unsure of this difficult
character, it is best to proceed with LBAM as a possibility.
3) Knowledge of separating males from females is required
to effectively use the key. 4) The costal fold is a sexual
character in tortricids, found only in the males of some
species, including LBAM. The uncus is spatulate (spoonshaped) in the LBAM but also a few common non-target
tortricids. 5) It is best to send forward any male specimens
with a membranous lobe on the valve. 6) Female LBAM
have a long straight ductus bursae and a corpus bursae with a
signum, but this combination is not unique. A common nontarget in California, Clepsis peritana (garden tortrix), has a
spiral ductus bursae; this character can often be seen through
the abdomen if the scales are brushed off while the specimen
is in alcohol or a cleaning agent.
Identification
Male LBAM can be distinguished by the large membranous
lobe extending laterally from the apex of the valve (Dugdale
et al. 2005) (Fig. 9). In addition, the base of the uncus is only
slightly narrowed (Fig. 8). Powell (1964) reports Clepsis
virescana as having a weak membranous lobe on the apex of the
valve; however, this lobe is much smaller than the lobe found in
LBAM and virescana males do not have a costal fold. Dugdale
et al. (2005) mentions the shape of the costal fold as a potential
character, but similarity to other species (like C. rosaceana) limits
its usefulness by non-specialists. Identification of LBAM based on
female genitalia is difficult and best left to specialists. Instructions
for submitting suspect LBAM specimens for identification are
outlined in the LBAM National Survey Guidelines.
Figure 12: Dorsal view of wing pattern
variation in LBAM adults.
References
Clarke, J. F. G. 1941. The preparation of slides of the genitalia
of Lepidoptera. Bulletin of the Brooklyn Entomological
Society, 36:149-161.
Dugdale, J. S., Gleeson, D., Clunie, L. H., and Holder, P. W.
2005. A diagnostic guide to Tortricidae encountered
in field surveys and quarantine inspections in New
Zealand: Morphological and molecular characters.
National Plant Pest Reference Laboratory. 161 pp.
Freeman, T. N. 1958. The Archipinae of North America
(Lepidoptera, Tortricidae). The Canadian Entomologist
90, Suppl. 7:1-89.
Passoa, S., Gilligan, T., and Epstein, M. 2007. Light Brown
Apple Moth (Epiphyas postvittana) Screening Aid.
http://www.tortricidae.com/lbamscreening.asp.
Powell, J. A. 1964. Biological and taxonomic studies on tortricine
moths, with reference to the species in California.
University of California Publications in Entomology.
Volume 32. 317 pp.
Robinson, G. S. 1976. The preparation of slides of Lepidoptera
genitalia with special reference to the Microlepidoptera.
Entomologist’s Gazette. 27:127-132.
Figure 13: Lateral view of wing pattern
variation in LBAM adults.
Acknowledgements
The authors would like to thank all of the coordinators of
the LBAM National Survey. Specifically, Richard Brown and John
Brown provided helpful comments regarding the identification of
LBAM specimens.
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Figure 14: LBAM adult on sticky trap.
Note partially visible mottled hindwing.